GLOSSARY
Proof of service
By Justin Winter · Updated August 28, 2026
A legal filing stating that a party was properly notified — usually a sworn declaration, supported by mailing evidence rather than replaced by it.
Proof of service is a court concept, not a postal product. The document is typically a declaration or certificate signed by the person who served, describing what was sent, to whom, how, and when.
Certified Mail with a return receipt is common supporting evidence because it dates the mailing and records the signature. What counts as proper service is set by the court or statute involved, so the mailing method has to match the rule rather than the other way round.
See also
- Proof of mailing — Documentation that a piece of mail was handed to USPS on a given date — the sending half of the evidence, not the delivery half.
- Certified Mail — A USPS extra service that adds a dated mailing receipt and delivery tracking to a letter, with the delivery record kept by USPS.
- Return receipt — A USPS add-on that sends the sender a copy of the recipient’s signature as proof the piece was delivered and to whom.
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